Lennie Briscoe grew up in the Meatpacking District of Manhattan.[8] He had a brother.[9] As a child, he attended P.S. 21, as his father had before him.[10] A veteran of two failed marriages, Briscoe has two daughters by his first wife, the elder Julia and the younger Cathy, and a nephew, Det. Ken Briscoe (played by Orbach's son, Chris). Cathy was born on June 23, 1971 and was murdered on March 4, 1998.[11] By 2002, he had at least two grandchildren.[12] He once walked into a bar and found his then wife kissing a man named Joe who lived down the street from them. He punched Joe several times and later claimed that he would have shot him if he had had his gun on him at the time.[13] Both of his marriages lasted for less than 11 years.[14]

He is a recovering alcoholic. He often makes references to being a "friend of Bill W." which is a reference to his having attended Alcoholics Anonymous. His drinking harmed his family; he was often absent from his daughters' lives, and they have distant, fractious relationships with him as adults. Briscoe blames himself, especially when Cathy, a methamphetamine addict, is murdered by a drug dealer after she testifies against the dealer in court.[19] However, he finds closure when the drug dealer dies from a heroinoverdose.[20] It is implied (although never explicitly stated) that Briscoe considered having the dealer killed. An old snitch of Briscoe's had offered to kill the dealer if Briscoe could get his charges reduced. Briscoe is later seen talking to the arresting officer about the snitch, but it is never confirmed if Briscoe did him the favor.[11] In the 1996 episode "Aftershock", after witnessing an execution from a case that he helped investigate, Briscoe falls off the wagon with disastrous results; A.D.A. Claire Kincaid (Jill Hennessy) is struck and killed by a drunk driver while driving him home from a bar.[21] The experience shakes him deeply, and he remains sober for the rest of his life.

Though not actually Jewish according to the traditional definition, Briscoe is sometimes the target of antisemitism from criminals and even some of his own colleagues and sometimes accused of "Jewish conspiracy" by criminal defense attorneys. Briscoe also develops a friendship with one of the few featured Jewish police officers during his tenure, John Munch (Richard Belzer), despite Munch's initial resentment when he discovers Briscoe had slept with his first wife Gwen.[30][31][32]

Briscoe is one of many characters on the show to have served in the military; he was at one point a corporal in the United States Army. On several occasions he has referred to his service in the Vietnam War. After leaving the Army, Briscoe joined the NYPD in the 29th Precinct in Manhattan and walked a beat there with stops at the 31st and 33rd Precincts, also in Manhattan, and the 110th and 116th Precincts in Queens, at some point reaching the rank of detective. It is also revealed in the 1999 episode "Marathon", that he spent three years in the Anti-Crime Unit. Briscoe's detective shield number is 8220.

Briscoe typically has a wise-crack or joke about the victim or circumstances of death at the close of the opening scene, with the joke usually exhibiting a very deadpan delivery while at the same time being highly "on target." He likes music, but mostly music that was popular in his youth. In one episode, Curtis chides his musical taste for stopping with Bobby Darin.[35] Briscoe used to read Langston Hughes back when he was a beatnik "for about five minutes" and "it used to work pretty good on Jewish girls."[36]

Many of Briscoe's former partners and colleagues outside the series (offscreen before Briscoe joined the 27th Precinct) have been or ended up becoming corrupt. In the 1993 episode "Jurisdiction", Lieutenant Brian Torelli (Dan Hedaya) forced a confession from a mentally handicapped man; at the end of the episode Briscoe is present when Internal Affairs arrests Torelli for suborning perjury and obstruction of justice.[37]

In the 1994 episode "Kids", the son of police Detective Ted Parker, a former colleague of Briscoe, is arrested for shooting another teenager. Parker and Briscoe have a private conversation where Parker uses hypothetics to virtually confess to Briscoe that his son only shot in self-defense. At the end of the episode, Parker tacitly acknowledges to Briscoe that he used his contacts in his old precinct to engineer the shooting death of a key prosecution witness in his son's case (resulting in a mistrial).[38]

Another of Briscoe's former partners, Detective John Flynn (Kevin Conway), falsely implicates him in the 1996 episode "Corruption" for taking seized drugs from the 116th Precinct evidence room (given to him by Flynn) during their stint there several years before. Flynn makes this allegation partly to throw off the Hellman Commission, which had been convened to investigate police corruption, including the questionable shooting death of a suspect by Flynn himself at the start of the episode, and partly as revenge against Curtis, who refused to falsely defend Flynn. Briscoe, however, has an alibi—he was having an affair with Officer Betty Abrams (Caroline Kava), a married woman. Against Briscoe's wishes, Abrams testifies before the commission to exonerate him. Because of the affair, however, the commissioners question her credibility. Briscoe finally gets the truth out of Flynn with a hidden wire, but Flynn commits suicide before he can be further prosecuted.[3] Although Briscoe is ultimately cleared, defense attorneys exploit the allegations for the rest of his career.[19][39][11][40]

In the 2000 episode "Amends", Briscoe has another reunion with one of his former colleagues that opens up some ugly history. While investigating a 20-year-old cold case, Briscoe learns that one of his former bosses, Tommy Brannigan (Brad Sullivan), had been convinced by his superior to accept bribes that helped promote him to lieutenant in exchange for letting a murder suspect go free. The now-retired Brannigan ultimately confesses to this in court, which helps McCoy in convicting the suspect of the cold case. Later, Briscoe visits Brannigan at his home, partly fearing that his old friend may have killed himself (just like Flynn) over his shame, but to his relief finds Brannigan alive and well repairing his lawnmower. When Brannigan asks Briscoe if he forgives him for what he had done, Briscoe replies "All day long, Tommy. All day long."[41]

There are moments in Briscoe's career where his decisions are controversial. In the 1998 episode "Stalker", a stalker accused of murdering a woman could have gone free because the police concluded that the victim had earlier lied to the police about previously being attacked by the stalker, thereby undermining the victim's credibility. However, after the victim is found murdered, Briscoe approaches McCoy and tells him that he now believes that the victim did not lie to the police of the stalker's earlier attacks and that he is willing to take the stand and state that the original police report was incorrect. His then-partner Rey Curtis was called by the defense to testify that he thought the original police report was correct. At the end of the episode, the stalker is found guilty; outside the courtroom, Curtis and Briscoe reconcile.[42]

Shortly after Ed Green is assigned as his partner, he and Briscoe nearly come to blows during a particularly difficult investigation of a robbery-homicide in the 1999 episode "Marathon". Their primary suspect confesses as he is being arrested, but because Briscoe is the only officer within earshot, Green, Van Buren and McCoy are placed in a difficult position with regard to the confession. Again, Briscoe is eventually vindicated, and he and Green work to rebuild their professional rapport and what eventually ends up as a close friendship.[43]

Briscoe retires in the 2004 episode "C.O.D." after 12 years at the 27th Precinct and more than 30 years in the NYPD.[44] His successor at the 27th Precinct is Det. Joe Fontana (Dennis Farina), whose stint there would be far shorter than Briscoe's.

Briscoe died at some point between 2004 and 2005 (Orbach himself died on December 28, 2004). Although not addressed directly in the main series until 2008, his death was implied in 2005 and confirmed in 2007 in Criminal Intent (see "Death" section below).

In 2005, the Lennie Briscoe character was written out after the second episode of Trial By Jury coinciding with Orbach's death on December 28, 2004 from prostate cancer. The character's departure from the show was originally to be in the episode "Baby Boom" where members of the DA's Office attend a memorial service for him. This scene was in fact filmed but never actually made it into the episode before its airing.

In the 2005 Law & Order: Criminal Intent episode "Diamond Dogs", Mike Logan, questioning a burglar's fence in a pool hall, is clearly referring to Briscoe when he says that a former partner was a "wizard with the stick".[45] In the 2007 Criminal Intent episode "Renewal", Logan says that Briscoe has died but he still sees him alive in his dreams.[46]

In the 2008 Law & Order episode "Burn Card", Ed Green says that he returned to gambling briefly after Briscoe died.[47] In the 2008 Criminal Intent episode "Last Rites", a Catholic priest who had known Briscoe approaches Logan after a prisoner's deathbed confession to a 16-year-old double murder in The Bronx.[48]

In the 2009 Law & Order episode "Fed", Rey Curtis returns to New York to bury his deceased wife Deborah, who had finally succumbed to multiple sclerosis, next to her parents. He reveals to Lieutenant Van Buren that he had spoken with Briscoe a few days before his death, and that he was his old wisecracking self right up to the end.